The frying process consists in placing a food in hot oil or fat at a temperature of 150-200° C. The oil acts a means through which heat is transferred to the fried product.
The frying process can be divided in two types: shallow frying and deep frying. With regard to the shallow frying, frying pans are generally used, where the level of oil used does not cover the food totally; thus, the food is fried over the surface in contact with the oil, and is cooked over the surface that does not touch the oil. On the contrary, in the deep frying, the food is totally submerged in the oil, so it is fried over the entire surface.
It is widely known how difficult is to handle foods at the moment of frying, since when those foods are introduced in the hot oil, the water contained in the food is instantaneously evaporated. Water evaporated carries oil and food particles, which may entail possible burns by the user, oil and food wastes, and soiling of the frying area.
The water contained in the food may come from the intrinsic humidity of the food or from the ambient humidity where the food has been stored. The water coming from the ambient may be in solid or liquid state, depending on whether the food has been refrigerated, frozen or stored at normal ambient conditions.
When the food is placed in the oil, the humidity related with the ambient is the first one that reacts and evaporates immediately. Vapor generated gets immediately in contact with the oil, causing both means to interact as a result of an interfacial force, which is relatively high as regards the conditions of this phenomenon. In this way, when the vapor column goes out, a certain amount of oil remains linked to the vapor, causing frying spattering.
In the case of the food intrinsic humidity, the water is evaporated slowly without causing significant frying spattering. This happens because the natural humidity of the food is slowly released from it, and in minimal amounts, and because the internal heating of the food is gradual and the water must travel a certain distance before its release.
In the state of the art, different types of anti-spattering agents for water-in-oil emulsions are distinguished (especially, for margarines and spreadable oils). Canadian patent CA 2077566 discloses an anti-spattering agent comprised of a mixture of partially oxidized soybean oil (“blown soybean oil”) and a source of phosphatides and salt to be used in spreadable oils. This reference is focused on reducing both primary (characteristic of emulsions) and secondary spattering (characteristic of the food to be fried).
On the other hand, international publication WO 2005/058066 discloses a water-in-oil emulsion containing a porous vegetable material with an average particle size of 1-2000 μm and a reducing spattering effect when it is used as a frying means. This porous vegetable material derives from fruits, nuts, seeds and/or grinded cellulose.
Reference WO 01/35756 discloses an anti-spattering agent for water-in-oil fluid emulsions, which comprises a mixture of different anti-spattering emulsifier agents, such as hydrolyzed lecithin, fractioned lecithin, citric acid esters, and mixtures thereof.
European patent EP 0013053 discloses the process for the production of margarine with a tendency of reducing spattering by adding separately a phosphatide, and a metal hydrophilic oxide and/or slightly divided metal oxide, in the oily phase.
As it is noted from the above-mentioned examples, little is known about agents or mechanisms for reducing spattering during food frying, when non-emulsified oily products are used as frying means, that is, pure edible oils or fats.
An exception to this is U.S. Pat. No. 3,415,659, which discloses oil for use as a means in food frying with anti-spattering properties or for use as a dressing. Substances providing oils with anti-spattering properties include: ethoxylated unsaturated fatty acid polysorbate with about 20 moles ethylene oxide containing from about 0.125% to 0.3% of total composition of the oil, and about 0.05% to 0.20% polyglycerol polyester of unsaturated fatty acids. The fatty acid of both compounds contains about 14-18 units of carbon. Those compounds are used as emulsifiers in water-oil systems. The anti-spattering principle of this oil is precisely the emulsion produced between the water from food articles and the oil. This principle has several disadvantages. The first disadvantage is the restriction in the emulsifying system dosage, in that with doses higher than the ones described in this document, the oil loses one of its basic properties, such as transparency, causing evident turbidity when the oil is subject to temperatures lower than 30° C. after frying. Another disadvantage is the possible formation of scum during the frying process, particularly, when high starch foods are fried.
Surprisingly, the inventors of this anti-spattering agent found that the system formed by vegetable oil, a hydrophilic colloidal metal oxide, a hydrophobic treated metal oxide, and a mixture of propylene glycols, when added to pure edible oils or fats, provides same with a low spattering property if said oils and fats are used in shallow or deep frying.
The anti-spattering agent described in this invention does not alter the organoleptic properties or appearance of the oil or fat, such as smell, taste, color, transparency and stability at low temperatures, or produce any negative effects, such as the formation of scum during frying or the presence of particles.